The present invention concerns a method for manufacturing and assembling photovoltaic cells in silicon on a metal substrate.
Making photovoltaic cells in crystalline silicon on silicon plates in the same way as integrated circuits is known. Such cells are relatively expensive and the surface thereof is limited to several tens of mm2. Moreover, they cannot be set in series directly on the base plate since the latter forms a common electrode for all the cells. They must first of all be separated by sawing, then assembled and electrically connected on an interconnection support, for example a printed circuit. Such a stamping method is disclosed for example in Japanese patent application JP-A-62025463. Sawing takes place after the silicon plate has been bonded to a drumskin on which the cells remain fixed, which facilitates the handling thereof during assembly.
Photovoltaic cells can also be made by depositing layers of amorphous silicon on a substrate ad hoc, for example, made of glass. This method is advantageous since it allows cells with a larger surface to be economically obtained. Moreover, it is possible to make cell assemblies in series directly on the glass support. However, for certain applications, the glass is too fragile, especially if its thickness has to be reduced to less than 1 mm. The support on a metal base, for example made of stainless steel, then represents a very interesting alternative. However, the fact that the base is conductive, unlike glass, poses a certain number of difficult problems, especially as regards setting the cells in series.
The object of the present invention is to overcome these problems.
More precisely, the invention concerns a method for manufacturing and assembling individual silicon photovoltaic cells on a metal substrate, characterised in that it includes the operations of:
making a metal plate provided with cut out portions delimiting the bases of a plurality of individual cells, said cut out portions being connected to each other and to said plate by points of attachment;
depositing on said plate a stack of silicon layers;
depositing on said stack a substantially transparent conductive layer, sparing at least the zones facing the points of attachment and if required, the adjacent zones of the cut out portions so as to form a set of individual photovoltaic cells which are electrically separated both from each other and at their top electrode formed by said conductive layer;
removing a group of individual cells from said assembly by perforating the points of attachment connecting said group to said metal plate;
transferring and securing the removed group of cells onto an interconnection support;
perforating the points of attachment still connecting the cells of said group to each other so as to separate them electrically at their bottom electrode formed by said metal plate; and
interconnecting said cells.
According to a first variant, the method according to the invention is characterised in that it includes the operations of:
making a metal plate provided with cut out portions delimiting the bases of a plurality of individual cells, said cut out portions being connected to each other and to said plate by points of attachment;
depositing a stack of silicon layers on said plate;
depositing on said stack a substantially transparent conductive layer sparing at least the zones facing the points of attachment and if required, the adjacent zones of the cut out portions so as to form a set of individual photovoltaic cells which are electrically separated both from each other and at their top electrode formed by said conductive layer;
removing a group of individual cells from said assembly by perforating the points of attachment connecting said group to said metal plate;
transferring and provisionally securing the removed group of cells onto an interconnection support;
perforating the points of attachment still connecting the cells of said group to each other so as to separate them electrically at their bottom electrode formed by said metal plate;
transferring and securing said cells one by one onto an interconnection support, and
interconnecting said cells.
According to a second variant, the method according to the invention is characterised in that it includes the operations of:
making a metal plate provided with cut out portions totally freeing the bases of a plurality of individual cells, said bases being then pushed back into the metal plate opposite said cut out portions;
depositing a stack of silicon layers on said plate;
depositing on said stack a substantially transparent conductive layer sparing at least the zones facing the points of attachment and if required, the adjacent zones of the cut out portions so as to form a set of individual photovoltaic cells which are electrically separated both from each other and at their top electrode formed by said conductive layer;
transferring and securing a group of individual cells onto an interconnection support;
removing said cells from the metal plate so as to separate them electrically at their bottom electrode formed by said plate; and
interconnecting said cells.
Finally according to a third variant, the method according to the invention is characterised in that it includes the operations of:
making a metal plate provided with cut out portions totally freeing the bases of a plurality of individual cells, said bases then being pushed back into the metal plate opposite said cut out portions;
depositing a stack of silicon layers on said plate;
depositing on said stack a substantially transparent conductive layer sparing at least the zones facing the points of attachment and if required, the adjacent zones of the cut out portions so as to form a set of individual photovoltaic cells which are electrically separated both from each other and at their top electrode formed by said conductive layer;
transferring and provisionally securing a group of individual cells onto an intermediate support;
removing said cells from metal plate so as to separate them electrically at their bottom electrode formed by said metal plate;
transferring and securing cells one by one onto an interconnection support; and
interconnecting said cells.
Advantageously, the method according to the invention also has the following features:
the operation of transferring and securing onto the interconnection support includes the electric connection of the metal base of the cells onto said support by means of a conductive adhesive material;
the cut out portions of the metal plate are made by stamping;
the interconnection of the cell is achieved by tapes including a plurality of parallel conductors electrically connecting contact zones of the cells to corresponding contact zones of the interconnection support via anisotropic conductive adhesive material.